Smithfield Plains is a northern suburb of Adelaide, South Australia in the City of Playford.
Smithfield Plains Post Office opened on 7 December 1967.
The John Hartley School B-7 school was built in the 2010s, replacing several earlier schools in the area. Around the same time, Smithfield Plains High School closed its campus in a merger to become part of Mark Oliphant College in nearby Munno Para.